Answer: The slope representing the relationship = 
 
 
Emily extract 7.5 liters oil after five days.
Explanation:
Let time in days is represented by 'x' and quantity of oil in liters is represented by 'y'. 
Assume Emily extracts essential oil at a constant rate.
Given statement :- Emily extracts 3 liters of essential oil for perfumes in two days.
We know that the slope of linear graph is the rate of change of y (dependent variable) with respect to x (independent variable).

⇒ The amount of oil Emily extracts after one day = 
 liters
 liters
Now, The amount of oil Emily extracts after five days = 
 liters
 liters